I’m
a bit concerned about this line of
questioning and some of what I noticed
happening at last week’s meeting (at least
the portion I was able to attend).
There
seems to be a lot of focus on
vendor-specific implementations which then
trends into the realm of cost comparison,
NDAs, and opinions on technical viability.
The
goal of the task force is to develop a
standard written such that it is not
dependent on any implementations, but rather
that it enables multiple, interoperable,
compliant implementations.
Is
it possible to put the relative cost
comparison and vendor-specific
implementation information aside and focus
on the market requirements and technical
merits of each proposal?
Thanks,
Brad
Dear all,
As a follow-up on yesterday’s discussion I am
summarizing here questions to the presentation
http://www.ieee802.org/3/bm/public/mar13/welch_01_0313_optx.pdf
Some of the questions I was able to ask during
the Q&A time, while some of them were left
unanswered or even not asked due to request of
the Chair to move the rest of the discussion
offline. Following Chair’s suggestion I am
writing down all the questions I was planning
to ask here in the Reflector. I do believe
that it is important for people on the floor
to get an unbiased view on advantages and
disadvantages of various proposals as well as
on technologies behind them to cast a balanced
educated vote.
The answer on the first question is crucial. I
would have had no further questions if the
answer would have been “Yes”. However the
answer was “No”. Correspondingly I feel
obligated to present here all the questions
numbered consecutively with the page number in
the presentation listed for the reference.
Page 1
Question 1
Do you agree or do you not, “yes” or “no”
would suffice, that “Si Photonics” in the
title of your presentation means “Luxtera Si
Photonics technology” and, correspondingly,
the numbers and statements presented are
related to advantages and disadvantages that
Luxtera technology has in trying to reach
performance required by different baseline
proposals?
Page 2
Question 2
This page represents the strategy for
comparative analysis of link budget, power,
assembly and cost for CWDM, PSM4 and LR4.
Depending on how this strategy is formulated a
substantially different set of conclusions can
be reached.
It is stated that for power estimate the
“fully integrated silicon photonics solution
using 28nm CMOS node” is being used. Does
“full integration” means CMOS circuits and
optical devices located side-by-side on the
same silicon die?
Question 3
What is the level of maturity of this “fully
integrated silicon photonics 28nm CMOS
technology” – a) is it in development, b) is
it fully qualified or, by any chance, c) does
Luxtera already have transceiver (not AOC)
products shipped today in volumes with this
technology node?
Question 4
In this page you mention “existing silicon
photonics technologies”. Which existing
silicon photonics technologies are you
considering: a) Luxtera technology exercised
in 130nm node at Freescale, b) Luxtera 28nm
technology mentioned above, c) any other
Luxtera technology not mentioned or d) Si
Photonics technologies of other companies?
Question 5
If the answer to Q4 is “all of the above”,
what are the sources of your information and
what is the approach you are using in
assessing the non-Luxtera Si Photonics
technologies?
Page 4
Question 6
Which technology version of Luxtera Si
Photonics technology the performance numbers
of WDM mux and Demux correspond to – a) the
130nm Freescale or b) “fully integrated
silicon photonics 28nm CMOS node”?
Question 7
How different is the interleaver presented on
the right bottom corner of this page from the
one reported in T.Pinquet et al, Proc. of SPIE
Vol. 6898, 689805, (2008) with 2.6dB insertion
loss?
Question 8
Are you aware of other reports on low-loss and
passive (no tuning power required) WDM filters
demonstrated in a number of non-Luxtera Si
Photonics technologies?
Question 9
For example, are you aware of several
presentations presented in the past at this
IEEE 802.3bm as well as in the 100G Study
Group meetings on WDM filters based on
non-Luxtera Si Photonics technologies that
have less than 3dB insertion loss:
pages 9 and 10 in
gill_01b_1112_optx.pdf
page 12 in
vlasov_01a_1112_optx.pdf
page 6 in
martin_01_0712_optx.pdf
page 4 in
vlasov_01_0312_NG100GOPTX.pdf ?
Question 10
Are you aware that of these WDM devices listed
in Q9 (in addition to many other silicon
photonics WDM demonstrations currently in the
public domain) NONE are relying on active
thermal tuning of the WDM components phase and
hence do not contribute to the total
dissipated power as it is demonstrated, for
example, on page 10 of
gill_01b_1112_optx.pdf ?
Question 11
Are you aware that all of these measured
results listed in Q9 are obtained on chips
fabricated on a high-volume non-Luxtera Si
Photonics technology platforms in Kotura or
IBM?
Question 12
Do you agree that the necessity to burn a
total of 1.8W of power for tuning of WDM
components as suggested in page 4 is not a
generic problem with all Si Photonics
technologies, but rather, perhaps, a problem
with one of Luxtera’s Si Photonics
technologies? Which one?
Page 5
Question 13
Does the “PSM4”, “CWDM” and “LR4” on the top
of each column have any relation to
corresponding baseline proposals as it was
presented at the latest meetings of 802.3bm (
anderson_01a_0313_optx.pdf and
vlasov_01a_0313_optx.pdf,)?
Question 14
The usual approach to calculate the optical
power link budget that 802.3 has followed for
many years is to calculate the channel
insertion loss between TP2 and TP3 and add the
TDP penalty. For all IEEE standards this link
budget does not include insertion loss of the
transmitter or receiver. These latter numbers
are left for vendors to resolve and are not a
part of any standard.
If the Q13 answer is “yes” then do you agree
that the link budget calculations should
follow the usual definition as channel
insertion loss plus TDP penalty for 500m
channel reach as presented for all PMD
baseline proposals so far?
Question 15
If the answer to Q13 is “yes” and the “CWDM”
column represent an attempt to build a channel
insertion loss budget based on the
100GBASE-CWDM baseline proposal (
vlasov_01_0113_optx
or
vlasov_01a_0313_optx) , why 2km option
is used on line 4 with additional 0.75dB
insertion loss, while the objective of both
the 802.3bm TF and the baseline CWDM proposal
is the reach up to 500m?
Question 16
If the answer to Q13 is “no” this means that
columns “CWDM” does not refer to a specific
baseline proposal. It is possible then to
assume that the table represents an attempt to
fold module insertion loss into the link
budget and compare to other solutions.
In this case, if the answer to Q4 is “all of
the above” and the answer to Q9 is “Yes” then
why additional 3dB+3dB=6dB insertion loss due
to MUX and DMUX is included for “CWDM” column
since it is a problem specific only to one or
all of Luxtera technologies in yielding low
loss WDM, and this generalization is not
applicable to all possible non-Luxtera Si
Photonics technologies?
Page 6
Question 17
If the answer to Q13 is “yes” and columns
“PSM4” and “CWDM” correspond to PSM4 and CWDM
baseline proposals as presented in
anderson_01a_0313_optx.pdf and
vlasov_01a_0313_optx.pdf,
correspondingly, then the bottom line of the
table representing “per baseline proposal
(aggregate)” corresponds to maximum channel
insertion loss. Correspondingly, for the
baseline PSM4 this should be 3.26dB and for
the baseline CWDM should be 4dB.
Correspondingly, the difference in channel
insertion loss between PSM4 and CWDM baseline
proposals should be 0.74dB, not 7dB. With
maximum TDP budgeted differently (for baseline
PSM4 as 3.8dB and for baseline CWDM as 2.2dB)
the total power link budget for maximum TDP is
actually 7.06dB for PSM4 and 6.2dB for CWDM.
Do you agree?
Page 8
Question 18
If the answer to Q1 is “Yes” there are no
comments related to pages 8, 9, 10, and 11
since it solely represents numbers for Luxtera
“fully integrated silicon photonics solution
using 28nm (or better) CMOS node.” The
maturity level of this technology is already
answered in Q3. If the answer to Q1 is “No” –
then there is a question: Which version of
non-Luxtera Si Photonics technology (and from
which company) is used to fill out the columns
“CWDM” and “LR4” in pages 8, 9, 10, and 11?
Page 12
Question 19
There is a subnote “Achilles heel of CWDM”.
Which non-Luxtera Si Photonics technologies
are having these problems?
Page 13
Question 20
Which non-Luxtera Si Photonics technologies
are having these problems?
For example edge coupling technologies are, in
fact, widely used for edge emitting lasers
iii-V PICs, etc. for many decades. Some of
non-Luxtera Si-Photonics technologies
successfully using edge coupling for volume
products, like for example VOA and other
components from Kotura. It is, actually,
vertical grating couplers that Luxtera
technology is using that is a relatively new
and to my knowledge unique approach for
coupling light in and out of the PIC.
In general, it is possible to imagine that
non-Luxtera Si Photonics technologies
utilizing edge coupling might not necessarily
suffer from violation of CMOS design rules, do
not require CMOS post-processing (precision
dice/polish), can enable easy fiber attach,
and do not require large area for bonding to
CMOS.
Question 21
If Luxtera Si Photonics technologies are being
used for comparison it would be good to know
which version of the technology a) 130nm
Freescale or b) “fully integrated silicon
photonics solution using 28nm (or better) CMOS
node” is being considered?
If it is a) then indeed millions of parts were
shipped and edge coupling was not in
production and is only theoretically known. If
it is b) then it is necessary to refer to the
answer to Q3 and apply it here with respect to
the statement “millions of grating couplers
already shipped”.
Question 22
What the source of the information that
non-Luxtera Si Photonics technologies using
edge coupling are having a problem of
“prohibiting chip on board cost reductions”.?
Question 23
What the source of this information that
non-Luxtera Si Photonics technologies that are
using edge coupling are having to rely on
“polarization maintaining fiber”?
Page 14
Question 24
If the answer to Q1 is “No” and the statements
on this page also include comments on
non-Luxtera Si Photonics technologies, then
the word “theoretically” should be removed
since numerous feasibility demonstrations have
been presented in the open public domain
showing monolithically integrated WDM mux,
Demux, photodetectors, modulators, etc. that
can be found for example in the proceedings of
the OFC from 2007 to 2013. I can easily
provide over 50 recent references upon
request.
Page 15
Question 25
If the answer to Q1 is “No” and the statement
on this page 14 “Insufficient technology
maturity to reasonably project costs/yields”
also includes comments on non-Luxtera Si
Photonics technologies, then I would insist on
rephrasing the statement to “Insufficient
information that Luxtera has on technology
maturity to reasonably project costs/yields”.
Page 16
It is a critical page in the presentation as
it compares module costs for various
implementations.
Question 26
If the answer to Q1 is “Yes” then don’t the
statements in this comparison refer to
problems specific to Luxtera Si Photonics
technologies, and as such this comparison
illustrates that Luxtera Si Photonics
technologies could not provide CWDM modules in
a cost-effective manner.
Question 27
If the answer to Q1 is “No” then the
statements in this comparison implies
generalization of problems specific to Luxtera
technologies to all other non-Luxtera Si
Photonics technologies. In this case I would
ask which non-Luxtera technology is used for
this comparison and what the source of this
information is. I would also suggest to take
into account three independent relative cost
analysis studies presented in
martin_02_0912_optx.pdf,
shen_01a_0313_smf and
in
vlasov_01a_1112_optx.
Page 17
Statements on this page either refer to
Luxtera Si Photonics Technologies (if the
answer to Q1 is “Yes”) or (if the answer to Q1
is “No”) it is required to provide additional
information as mentioned in all related
questions above.
Sincerely
yours
Yurii
Vlasov